1. Technical Field
The present invention relates to a printing apparatus, and a calibration method to be performed by the printing apparatus.
2. Related Art
Existing printing apparatuses that print images on a medium (paper, cloth, and so forth) are configured to print a pattern composed of a multitude of patches of different gradation levels on the medium, and read out the patches in the pattern with an optical sensor to thereby perform calibration on the basis of the reading result. For example, JP-A-2008-302521 discloses a technique of printing a pattern composed of a multitude of patches of different gradation levels and correcting the gradation level of the image to be printed, on the basis of the density of each patch that has been read, which is known as color calibration.
To perform the color calibration according to JP-A-2008-302521, it is necessary to detect the density of the patches with high accuracy. However, although the patches are printed in the same density, the optical sensor may output different read-out values depending on the position on the medium where the patch is printed. For example, in the case where a distance between a given point on the surface of the medium and the reading position of the optical sensor is different from the preset value, a different read-out value is outputted.